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  • Title: 1H, 13C and 19F NMR spectroscopy of polyfluorinated ureas. Correlations involving NMR chemical shifts and electronic substituent effects.
    Author: Abad A, Agulló C, Cuñat AC, Vilanova C.
    Journal: Magn Reson Chem; 2005 May; 43(5):389-97. PubMed ID: 15706610.
    Abstract:
    Seventeen N-(mono-, di-, tri-, tetra- and penta-fluorophenyl)-N'-(3-nitrophenyl)ureas were prepared and characterized. Complete assignment of their (1)H, (13)C and (19)F NMR data was undertaken and the correlation of the chemical shifts of the ureido protons with field-inductive and mesomeric electronic substituent parameters was studied using the Swain-Lupton model. The best correlations were obtained when the study was limited to certain substitution patterns, e.g. non-ortho, mono-ortho- and di-ortho-fluorinated ureas, which reveal probable changes in conformations caused by the degree of ortho fluorination at the phenyl ring. Additionally, there is an excellent linear cross-correlation between the chemical shifts of the fluorine atoms and the ipso carbon atoms for the whole group of fluorinated ureas.
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